Neomyxine n.g. based on Myxine biniplicata Richaidson and Jowett 1951 is distinguished by a slender form, ventral fold reaching to the branchial apertures, painted fin-folds extending from behind the branchial apeitines anteriorly, and a mucous gland count which is greater than the number of segments.
The original account of Myxine biniplicata Richardson and Jowett 1951 was based on one large dissected specimen and a second small and damaged specimen. From these, it was obvious that a new myxinid occurred in Cook Strait; but the condition of the material was such as to warrant only a conservative attitude towards its generic status. Since then, I have received through Mr. J. A. Garrick and through the master and erew of the fishing trawler “Maimai” operating out of Wellington, a further eight specimens, some alive, some frozen, some preserved. Examination of these has confirmed the original suspicion that a separate genus should be established with this species as the genotype, and Dr. Carl Hubbs has recommended this step to me. Certainly in spite of the strong general resemblance to Myxine, the presence of the additional lateral fin-folds, the high count of mucous pores, and the elongate slender form are characters which are of greater than specific value in other groups. Removing M. biniplicata, from the genus, leaves a relatively uniform group of species from which the Cook Strait, species is sharply set off as above. In the original preserved specimens, the extent of the lateral fin-folds and the origin of the ventral fin-fold were obscured by wrinkling and ridging of the skin so that the ventral fin-fold appeared to extend between and anterior to the branchial apertures. In live material, this fold falls just short of these apertures.
Three specimens were brought alive to the laboratory and placed in a 50-gallon aquarium tank in which the water was kept in circulation. These were generally lethargic, but two escaped from the tank in spite of a glass cover, the third was held alive for some weeks. The live specimen is somewhat faintly flesh-coloured, with faint olive-brown tonings which are not obvious in water, so that the animal appears white suffused with pink largely if not entirely due to the subeutaneous circulation of blood. The mucous glands are white. In preservative, the colour is from faint to a pronounced brown, generally that of coagulated preserved blood. The live animal does not exhibit black or other colours obviously related to chromatophores, and showed no change in colour during the period it was kept alive.
Neomyxine biniplicata (Richardson and Jowett) 1951.
Fig. 1.—Lateral view of head and pharyngeal region.
Fig. 2.—Lateral (B) and ventral (A) views of entire animal from a specimen 382 mm. total length, b.a., branchial aperture; 1., lateral, l.t., labial, n., nasal, and s.n., subnasal tentacles; l.f., lateral and v.f., ventral fin-folds; s.g., mucous glands.
In the tank, the animal was quiet over long periods. It then showed no sign of activity other than a persisting pulsation of the body-wall lateral to the pericardial chamber. During such periods, while resting on the bottom, the lateral fin-folds are spread as though pressing against the bottom of the tank, or as though the animal were maintaining its attitude by resting on these folds. Attempts to feed were unsuccessful although fresh and old meat and fish, and even a live fish were offered.
I am indebted to Mr. R. Barwick for Fig. 1.
Nani and Gneri (1951) have based a new genus Notomyxine on “Myxine” tridentiger Garman which they show possesses in addition to the pair of branchial apertures a separate opening from the oesophageo-cutaneous duct. This third aperture is posterior to the others. They present a figure (their Fig. 6) which is most valuable. In it, they show the ventral aspect of three species of Bdellostoma, a species of Paramyxine, Myxine garmani and Notomyxine tridentiger. The two latter have a strong resemblance in general proportions, in the level of the paired branchial apertures, the extension of the ventral fin-fold anteriorly so that it falls short of but nearly reaches the level of the branchial apertures, etc. Representing M. biniplicata in a similar manner, it appears as a more slender animal having a proportionately longer tail, with the ventral fin-fold reaching to the branchial apertures, and with the unique lateral fin-folds. Accordingly I propose this species as the type of a new genus in the Myxinidae, as follows: